Improved rock-drill



UNITED STATES STEPHEN F. GATES, OF BO STON, MASSAOHUSETTS.

IMPROVED ROCK-DRILL.

Specification forming part of'Letters Patent No. 55,277., dated June 5,1866.

To all 'whom it may concern:

Be it known that I, STEPHEN F. GATEs, of Boston, in the county ofSufiblk and State of Massachusetts, have invented an ImprovedRock-Drill; and I do hereby declare that the following, taken inconnection with the drawings which accompany and form part of thisspecification, is a description of my invention sufficient to enablethose skilled in the art to practice it.

In drillin g rock, especially when making use of mechanism to actuatethe drill, it is found Very difficult to ohtain a truly cylindricalhole.l It is not necessary to elaborate or state the reasons for this,or the theory governiu g this action of stone-drills,as thefact is wellknown to quarry and other practical men, the ordinary two-bladed orstraight-cut drill tending to make athree-sided hole, and thefour-bladed or cnoss-cut drill tending to form a five-sided hole. TheZ-drill is less liable to the objections named than are drills withradia-l blades equiangular from the center, but it is expensive inconstruction and difficult to repair.

The object of my invention is the production of round holes byrock-drills of simple and inexpeusive formation, my inventionvconsisting in irregulating the cutters of drills which radiate from acenter, so that the spacing on the periphery of the drill from cutter tocutter shall lack uuiformity. It is not necessary to give the reason whya drill thus irregulated will form, in action, a cylindrical hole, as itis proved in practice that round holes are the result of the action ofsuch irregulated drills, and that irregular or angular holes are theresult, in stone-drilling, of the action ot' drills formed withregularly-spaced radial cutters.

Figure l of the drawings shows, in side ele- Vation, one of my improvedrock-drills having four blades, and Fig. 2 shows a view of the Cuttingend thereof.

In Fig.2 it will be seen that two of the blades are left with theircutting-edges in the lines of radii at right angles to each other, whilethe two others are bent toward each other from such right-angledposition, so that of the angles inclosed by the cutting-blades one isl aright angle, one an acute angle, and the two others are obtuse angles.While in said illustration the eutters or edges made irregular are thosenearest each other, the result would be the sameif the opposite edges orcutters were the ones bent or swerved, and they might be thus bent orswerved to either side.

I claim A roek-drill when made with cutting-edges arranged substantiallyas and for the purpose specitied.

STEPHEN F. GATES.

Witnesses:

J. B.. ORosBY, F. GoULD.

